(1) Field of the Invention
The invention relates to field emission flat panel displays, and more particularly to structures and methods of manufacturing field emission displays that provide soft luminescence for improved end-user viewing characteristics.
(2) Description of the Related Art
In display technology, there is an increasing need for flat, thin, lightweight displays to replace the traditional cathode ray tube (CRT) device. One of several technologies that provide this capability is field emission displays (FED). An array of very small, conical emitters is manufactured, typically on a semiconductor substrate, and can be addressed via a matrix of columns and lines. These emitters are connected to a cathode, and surrounded by a gate. When the proper voltages are applied to the cathode and gate, electrons are emitted and attracted to the anode, on which there is cathodoluminescent material that emits light when excited by the emitted electrons, thus providing the display element. The anode is typically mounted in close proximity to the cathode/gate/emitter structure and the area in between is typically a vacuum.
FIG. 1 is a cross-sectional view of a typical field emission display of the related art. Row electrodes 12 are formed on an insulating baseplate 10, and have emitter tips 14 mounted thereon. The emitters are separated by insulating layer 16. A column electrode 18, or gate, with openings for the emitter tips, is formed on the insulating layer 16 and is formed perpendicular to the row electrodes. When electrons are emitted, they are attracted to conductive anode 22 and upon striking phosphor dot 20, light is emitted, which can be viewed through the transparent faceplate 24. However, the phosphorescence produced by this structure is not comfortable for the viewer of the display, since the light emission is directly at the viewer and the phosphorescence intensity distribution of each pixel is not uniform.
U.S. Pat. No. 4,908,539 to Meyer discloses a change in the location of the phosphor 30, from the faceplate to on top of the column electrode 18, as shown in FIG. 2. This eliminates the light loss in the FIG. 1 structure that occurs as the emitted light passes through the phosphor. Furthermore, alignment of faceplate and baseplate is no longer critical. However, this structure also suffers from the problem of non-uniformity of phosphorescence intensity.